
An airport would take a quickest several weeks to make
It depends from the complexity of the real thing and your willingness to commit to the project.
A small airport with one single runway and apron, and a small web of taxiways... less than a day with ADE9X. 8-)
More complexity means, of course, more time.
There are thousands :-?

This is sadly true. A project of redoing in a passable way all the airports and/or small strips that in the whole FS world M$ left as a single runway would be titanic at the very least. :-/
There is no such a thing as overkill. Only unworthy targets.